Design and Analysis of Kinematic Couplings for Modular Machine and Instrumentation Structures

For decades, kinematic couplings have been developed and used because of their astounding repeatability, but few efforts have been made to unify the design theory into a general strategy for widespread application of deterministic interfaces in flexible automation, where both repeatability and interchangeability are important. Accordingly, this thesis seeks to present a methodology for using kinematic couplings as deterministic interfaces for modular machine and instrumentation structures, with focus applications to design of an industrial robot factory interface and design of a next-generation microscope structure. Theory is presented for design of traditional ball/groove, canoe ball, traditional quasikinematic, three-pin quasi-kinematic, and cylinder/groove quasi-kinematic couplings. Furthermore, the ability to parametrize kinematic coupling performance is extended from reliance on experimental repeatability analysis to an estimate of Total Mechanical Accuracy, based on a closed-form computer model for determining the interchangeability of canoe ball and three-pin interfaces. With calibration of the interface by measurement of the perturbed locations of its contact points, introduction of an interface transformation to a machine’s structural loop can reduce the deterministic interchangeability error to essentially that inherent in the routine of the measurement system used for calibration. Perhaps more powerfully, a parametric model of interchangeability allows engineers to predict the accuracy of an interface, based on tolerance distribution parameters assigned to the coupling manufacturing process, plate manufacturing process, interface assembly process, and interface calibration process. This predictive ability enables choice of manufacturing process precision and calibration detail to give the desired interface accuracy at minimum cost. Modularity of structures based on kinematic couplings can also be exploited to provide flexibility through being able to interchange style-specific manufacturing tools without the need for re-calibration of machines, and as demonstrated by the microscope case study, significantly improved thermal performance for ultra high-precision applications. Looking forward, the ability to characterize performance of kinematic couplings in a closed form makes them well-suited for development of a standard representation for